Method for fabricating a thin film resistor semiconductor structure
A method is provided of fabricating a thin film resistor semiconductor structure. In one aspect of the invention, the method includes forming a dielectric layer over a semiconductor substrate, forming a thin film resistor on the dielectric layer, and annealing the thin film resistor at a substantially high temperature for a predetermined time period to set the thermal coefficient of resistance of the thin film resistor. A passivation layer is formed over the semiconductor structure.
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The present invention relates generally to semiconductor devices and, more particularly, to fabricating a thin film resistor semiconductor structure.
BACKGROUNDIn the semiconductor industry, there is a continuing trend toward higher device densities. To achieve these high densities, there has been and continues to be efforts toward scaling down device dimensions to submicron levels (e.g., below 0.35 microns) on semiconductor substrates. In order to accomplish such high device packing density, smaller and smaller features sizes are required. This may include the width and spacing of metal interconnecting lines, spacing and diameter of contact holes, and the surface geometry such as corners and edges of various features. Conventionally, analog precision and mixed signal devices have not been fabricated employing these submicron densities. This is because the precision of the analog devices and the selection of available materials for precision analog devices have been overriding factors over device density and device speed.
Conventionally, doped polysilicon is employed as a material of a resistor in a semiconductor fabrication. However, the resistance of a doped polysilicon resistor is controlled by the size of the predetermined length and area of the doped polysilicon layer. Therefore, to increase the resistance per unit of a resistor, thin film resistor materials are employed such as silicon chromium (SiCr) alloy, nickel chromium (NiCr) alloy, tantalum nitride, titanium nitride, and tungsten. Thin film resistors are very attractive components for high precision analog and mixed signal applications. In addition to a low thermal coefficient of resistance and low voltage coefficient of resistance, thin film resistors provide good resistor matching and good stability under stress. However, the thermal coefficient of resistance can shift during subsequent thermal processing of the thin film resistor.
SUMMARYIn one aspect of the present invention, a method is provided for fabricating a thin film resistor semiconductor structure. The method comprises forming a dielectric layer over a semiconductor substrate, forming a thin film resistor on the dielectric layer, and annealing the thin film resistor at a substantially high temperature for a predetermined time period to set the thermal coefficient of resistance of the thin film resistor. A passivation layer is formed over the semiconductor structure.
In another aspect of the present invention, another method is provided for fabricating a thin film resistor semiconductor structure. This method comprises forming a dielectric layer over a semiconductor substrate, forming a thin film resistor material layer on the dielectric layer, forming a barrier layer over the thin film resistor material layer, forming a capping layer over the barrier layer and etching away portions of the capping layer, the barrier layer and the thin film resistor material layer to form a thin film resistor structure. The method further comprises removing the capping layer, forming a contact material layer over the thin film resistor structure, and etching the contact material layer except at contact ends of the thin film resistor structure. The thin film resistor structure is annealed at a temperature of about 450° C. to about 550° C. for a predetermined time period to set the thermal coefficient of resistance of the thin film resistor within a range of about +/−5 ppm/° C., and a passivation layer is formed over the semiconductor structure.
In yet another aspect of the invention, yet another method is provided for fabricating a thin film resistor semiconductor structure. This method comprises forming a dielectric layer over a semiconductor substrate, forming an opening in the dielectric layer to a device in the semiconductor structure, forming a thin film resistor adjacent the opening on the dielectric layer, and forming a contact material layer over the thin film resistor structure and the dielectric layer, wherein the contact material layer couples the thin film resistor to the device in the semiconductor structure. The contact material layer is etched away except at contact ends of the thin film resistor. The thin film resistor is annealed at a temperature of about 450° C. to about 550° C. for about 15 minutes to about 25 minutes to set the thermal coefficient of resistance of the thin film resistor within a range of about +/−5 ppm, and a passivation layer is formed over the semiconductor structure.
The present invention relates generally to a method of fabricating a thin film resistor semiconductor structure. The method includes performing a temperature anneal at a substantially high temperature for a predetermined time period during the fabrication process to substantially stabilize the thermal coefficient of resistance of the thin film resistor. A substantially high temperature is defined herein as a temperature that is between about 400° C. to about 600° C. (e.g., about 500° C.). The time period for temperature anneal can range between about 10 minutes to about 60 minutes. The annealing process sets the temperature coefficient of resistance (TCR) of the thin film resistor to be within a range of about +/−5 ppm/° C. The TCR is a measure of the rate at which a resistor value varies with increasing or decreasing temperature and can be defined as follows:
TCR=((R2−R1)/R1(T2−T1))*10−6 EQ. 1
where TCR is the temperature coefficient of resistance in ppm/° C., R1 is the resistance at low temperature T1 (e.g., 45° C.), R2 is the resistance at high temperature T2 (e.g., 145° C.). While the following description of the present invention is illustrated with respect to the structure shown in
In one aspect of the present invention, the oxide layer 52 is formed using at least one of TEOS silicon oxides, PECVD silicon oxides, silicon nitrides, silicon oxynitrides, silicon carbides, spin-on glass (SOG) such as silsesquioxanes and siloxane, xerogels or any other suitable material. The field layer 52 can be planarized by a chemical mechanical polish (CMP).
A photoresist layer (not shown) is formed and patterned over the oxide layer 52. An etch 100 is performed on the oxide layer 52 underlying the photoresist layer to form a via or contact 56 (
A barrier layer 60 is then deposited over the thin film material resistor layer 58. The barrier layer 60 can be formed from titanium tungsten (TiW) or titanium nitride (TiN). A capping layer 62 is then formed over the barrier layer 60. The capping layer 62 can be formed, for example, from an aluminum copper alloy (e.g., 99.5% aluminum, 0.5% copper).
An etch 110 (
Following the formation of the TFR structure 64, a subsequent etch 120 is performed, as illustrated in
Following the formation of the contact material layer 68, a patterned photoresist (not shown) is formed over the contact material layer 68, and is used as a pattern to remove a portion 66 of contact material layer 68 (
Turning now to
Following the annealing process, a passivation layer 74 is formed over the semiconductor structure as illustrated in
What has been described above includes exemplary implementations of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims.
Claims
1. A method for fabricating a thin film resistor semiconductor structure, the method comprising:
- forming a dielectric layer over a semiconductor substrate;
- forming an opening in the dielectric layer to the semiconductor substrate;
- forming a mesa dielectric layer over the dielectric layer and the opening in the dielectric layer;
- forming a thin film resistor material layer on the mesa dielectric layer;
- forming a capping layer over the mesa dielectric layer;
- etching portions of the capping layer and the thin film resistor material layer to form a thin film resistor structure;
- removing the capping layer;
- etching portions of the mesa dielectric layer to form an opening in the mesa dielectric layer at least at the opening in the dielectric layer, leaving portions of the mesa dielectric layer beneath the thin film resistor structure remaining;
- forming a contact material layer over the thin film resistor structure and the opening in the mesa dielectric layer;
- etching a portion of the contact material layer overlying a central portion of the thin film resistor structure except for contact ends of the thin film resistor; and
- annealing the thin film resistor structure at a temperature of about 400° C. to about 600° C. in an inert gas ambient for a time period of about 10 to about 60 minutes to set the thermal coefficient of resistance of the thin film resistor structure to be within a range of about +/−5 ppm/° C.
2. The method of claim 1, wherein the time period comprises about 15 minutes to about 25 minutes.
3. The method of claim 1, further comprising forming a barrier layer over the thin film resistor material layer; wherein forming the capping layer comprises forming the capping layer over the barrier layer; and wherein etching portions of the capping layer and the thin film resistor material layer to form the thin film resistor structure comprises etching portions of the capping layer, the barrier layer and the thin film resistor material layer to form the thin film resistor structure.
4. The method of claim 3, wherein the time period comprises about 30 minutes to about 50 minutes.
5. The method of claim 3, wherein etching the portion of the contact material layer includes etching a portion of the baffler layer overlying the central portion of the thin film resistor structure except for the contact ends.
6. The method of claim 1, wherein the opening in the dielectric layer is an opening to a device in the semiconductor substrate; and wherein the contact material layer couples a first end of the thin film resistor structure through the opening in the mesa dielectric layer and the opening in the dielectric layer to the device in the semiconductor substrate.
7. The method of claim 1, wherein the thin film resistor material layer is formed from one of silicon chromium (SiCr) alloy, nickel chromium (NiCr) alloy, tantalum nitride, titanium nitride, and tungsten.
8. A method for fabricating a thin film resistor semiconductor structure, the method comprising:
- forming a dielectric layer over a semiconductor substrate;
- forming a thin film resistor material layer over the mesa dielectric layer;
- forming a baffler layer over the thin film resistor material layer;
- forming a capping layer over the baffler layer;
- etching portions of the capping layer, the barrier layer and the thin film resistor material layer to form a thin film resistor structure;
- removing the capping layer;
- forming a contact material layer over the thin film resistor structure;
- etching a portion of the contact material layer overlying a central portion of the thin film resistor structure except for contact ends of the thin film resistor;
- annealing the thin film resistor structure at a temperature of about 500° C. in a nitrogen (N2) ambient for a time period of about 10 to about 60 minutes to set the thermal coefficient of resistance of the thin film resistor structure to be within a range of about +/−5 ppm/° C.; and
- forming a passivation layer over the semiconductor structure; further comprising:
- forming an opening in the dielectric layer to the semiconductor substrate;
- forming a mesa dielectric layer over the dielectric layer and the opening in the dielectric layer prior to forming the thin film resistor material layer; and
- forming an opening in the mesa dielectric layer by etching portions of the mesa dielectric layer such that only portions of the mesa dielectric layer beneath the thin film resistor material remain prior to forming the contact material layer over the thin film resistor structure.
9. A method for fabricating a thin film resistor semiconductor structure, the method comprising:
- forming a dielectric layer over a semiconductor substrate;
- forming a contact opening in the dielectric layer to a device in the semiconductor substrate;
- forming a mesa dielectric layer over the dielectric layer and the opening in the dielectric layer;
- forming a thin film resistor material layer on the mesa dielectric layer;
- forming a baffler layer over the thin film resistor material layer;
- forming a capping layer over the baffler layer;
- etching portions of the capping layer, the barrier layer and the thin film resistor material layer to form a thin film resistor structure;
- removing the capping layer;
- etching portions of the mesa dielectric layer to remove portions of the mesa dielectric layer from over the dielectric layer and the opening in the dielectric layer, leaving portions of the mesa dielectric layer beneath the thin film resistor structure remaining;
- forming a contact material layer over the thin film resistor structure and the opening in the dielectric layer;
- etching a portion of the contact material layer and a remaining portion of the previously etched barrier layer overlying a central portion of the thin film resistor structure except for contact ends of the thin film resistor structure; wherein the etched contact material layer couples a first end of the thin film resistor structure through the opening in the dielectric layer to the device in the semiconductor substrate;
- annealing the thin film resistor structure at a temperature of about 400° C. to about 600° C. in a nitrogen (N2) ambient for a time period of about 10 to about 60 minutes to set the thermal coefficient of resistance of the thin film resistor structure to be within a range of about +/−5 ppm/°C.; and
- forming a passivation layer over the semiconductor structure.
Type: Grant
Filed: Jul 11, 2005
Date of Patent: Mar 2, 2010
Patent Publication Number: 20070008062
Assignee: Texas Instruments Incorporated (Dallas, TX)
Inventors: Joseph D. Fivas (Midvale, UT), Georgina Shah (Tucson, AZ), Dianna L. Chandler (Tucson, AZ)
Primary Examiner: Thiem Phan
Attorney: Warren L. Franz
Application Number: 11/178,673
International Classification: H01C 17/00 (20060101);